Multianode cathode-ray tube circuit having a rapid flyback action



N 4, 1952 P. H. DE BEURS 2,617,074

MULTIANODE CATHODERAY TUBE CIRCUIT HAVING A RAPID FLYBACK ACTION Filed Dec. 22, 1950 INVENTOR. PIETER HENDRIK DE BEURS AGENT Patented Nov. 4, 1952 M ULTIAN ODE CATHODE-RAY TUBE CIRCUIT HAVING A RAPID FLYBACK ACTION Application December 22, 1950, Serial No. 202,346

In the Netherlands February 14, 1950 4 Claims.

This invention relates to a circuit-arrangement comprising a cathode-ray tube provided with means for producing and deflecting an electron beam and in which a collecting electrodesystem is coupled to the deflection means for the beam so that the beam may occupy a number of naturally stable positions, means being provided for shifting the beam from one stable position to another.

In a known circuit-arrangement of this type, the cathode-ray tube comprises collecting electrodes which are arranged side by side in the direction of deflection and connected to taps on a potentiometer, an additional tap being coupled to a deflection electrode of the tube, and the taps being so chosen that if the beam strikes one of the collecting electrodes the deflection voltage produced is just suflicient to direct the beam to the electrode in question.

In a further known circuit-arrangement, the beam is kept in difierent stable positions, since in each of these positions the beam current is divided over a first collecting electrode and one or more further collecting electrodes, the first collecting electrode being on the one hand connected directly to a deflection electrode and on the other hand to a voltage source through a resistor. In a state of equilibrium, such a part of the beam current passes to the first collecting electrode and through the resistor as to produce the deflection voltage corresponding with this position, a slight deviation from this position involving a reaction of the deflecting field so that the beam is shifted back to the stable position.

Consequently, different deflection voltages correspond to different stable positions of the beam. The beam can be shifted from. one stable position to another by supplying an impulse to the deflection system. Such circuit-arrangements are particularly suitable for counting purposes, for example in calculating apparatus, since the position of the beam is an indication of the number of pulses supplied to the circuit-arrangement.

The number of stable positions is, say ten, so that the number of pulses may be registered on the decimal scale. In order to move the beam back to a given initial position, after all stable positions have been passed in succession, for example after every tenth impulse, a known circuit-arrangement comprises an auxiliary collecting electrode which is provided laterally from the main collecting system in the tube. This auxiliary electrode is struck by the beam in an extreme position and an impulse is produced within this electrode. This impulse is supplied to the deflection system or to an intensity-control electrode of the tube and effects the flyback of the beam. Upon every flyback an impulse is furthermore supplied to a circuit arrangement registering the tens,'for example.

It is known to use a secondary-emission auxiliary collecting electrode.

Furthermore, it has been proposed to couple the auxiliary collecting electrode capacitatively to a deflection electrode.

In order that the circuit-arrangement may act as rapidly as possible, it is desirable that flyback should take place very rapidly.

The present invention provides a circuit-arrangement which permits this aim to be achieved by simple means and without using auxiliary tubes.

According to the invention, a circuit-arrangement comprising a cathode ray tube provided with means for producing an electron beam and means for deflecting the beam in a particular direction and in which a collecting electrode system is coupled to the deflection means so that the beam may occupy a number of naturally stable positions, means being provided for shifting the beam from one stable position to another, a secondary-emission collecting electrode being arranged in the tube in such manner that it is struck by the beam in an extreme position of the beam, which collecting electrode is coupled to a voltage source through at least one resistor and means being provided which respond when the secondary-emission collecting electrode is struck by the beam to return the beam from the extreme position to an initial position, is char acterized in that a further collecting electrode "is provided in the proximity of the secondaryemission collecting electrode, this further collecting electrode being coupled capacitatively to a deflection electrode and coupled by way of at least one resistor to a voltage source such that if the secondary-emission collecting electrode is not struck by the beam, the potential of the further-collecting electrode exceeds that of the secondary-emission collecting electrode, and the said deflection electro e has a sense of deflection such that the beam is shifted in the direction of the initial position if the potential of this electrode is increased.

The secondary-emission collecting electrode may furthermore be coupled capacitatively to an intensity control electrode of the tube, the intensity control electrode being coupled to a voltage source through at least one resistor.

in order that the invention may be more clearly understood and readily carried into effect, it will now be described more fully with reference to the accompanying diagrammatic drawin given by way of example, in which;

Fig. 1 shows one embodiment of the circuitarrangement according to the invention.

Fig. 2 is a current-voltage diagram with reference to which the operation of the circuitarrangement will be explained. W

The cathode-ray tube l shown in *Fig.1#comprises a cathode 2, a control grid 3, means 4 for producing an electron beam remthe electrons emitted by the cathode 2, deflection -pla tes 5 6 and collecting electrodes 1, 8, l2 and 13. The means 4 are coupled, in a manner-not--'shown,'to suitable taps On a supply battery 11. The "electrode 1 is arranged in front of, i. e. on the cathode side of the electrode 8 and provided with apertures I so that the beam, upon deflection, alternately strikes an element bf -the 1ee'trede I and, through the apertures I provided inthe electrode 1, the electrode 8. The current flowing to the electrode '8, as adu'n'ction of'ftlie deflection voltage set up at thedeflettien enetreae 6 then has the form of the curve 2| '"s'h'o'v'vn i'n Fig. 2. If the beam passes through a'naperture in the electrode 1 substantially the w ole beam current passes to the electrode 8. If however,

the beam is intercepted by the electrode 1, the

current flowing to the electrode 8 is'sub'stantially zero. The electrode 8 is connected by way of a conductor 9 to the deflection electrode 'swm'eh is furthermore coupled through a resistor Into the positive terminal of the battery H. The

negative terminal of the battery'i's connected to the cathode 2 of the cathode-ray'tube. The collecting electrode 1 is connected directly toj'the positive terminal of the battery H. The deflection electrode 5 is connected 'to a tap on 'the battery ll.

The relationship existing between the current through the resistor 10 and the voltage of the electrode 6 is shown in Fig. 2 by the straight line If no current passes through the resistor ID, the voltage at-point l6 -cor respondsto the battery voltage and with current flow the voltage drops below this value. In "a state of equilibrium, the current through the conductor 9 is cqual'to the current through the resistor t!) which means that the positionsof equilibrium of the beam must correspond with i ntersections of the curves 20 and 2i shown in Fig.2. The intersections 23, 24, 25, 26, 21 and 2 8 correspond to stable positions of the beam, the intersections 29, 30, 31,32, 33 and 34 corresponding with unstable positions of equilibrium. This-maybe explained as follows; p r a L Suppose the voltage at ;point -IB is equal to V2 at a given instant. The current -passing through the conductor '9 then exceeds thecurrent through the resistance !0. Due to the c urrent difference the capacity C (Fig. -1) which is connected between point l6 andground-is discharged. The capacity may be stray capacityor provided in part by a capacitor. -Herice,=the voltage at It will drop=and the beam will move in the direction of the stable beam position corresponding with the intersection 25. The same holds if the voltage at It is slightly lower than j the voltage V1 corresponding with the'intersection 25. Consequently; the -beam will automatically assume this stable position 'iffthe voltage at 16 lies between the voltages V3 and V4 orresponding with th'e metastabiepcsitifis of eqin- 4 librium 32 and 3|. so that this interval is the area of attraction of the stable position 25.

Similarly, voltages exceeding the voltage V5, which corresponds to the metastable position 29. belong to the area of attraction of the initial position 35. Consequently, if for some reason the "voltage at point l6 exceeds voltage Vs,--the beam moves to the right until reaching the position 35. It is to be noted that if the resistance line 20 "is shifted to the left with respect to the curve 2|,

- for example, by variation of the battery voltage,

so that the intersection between the straight line loans the axis of the voltage is at a voltage lowerthan Vs, for example at V5 the beam will assume the position 23 if a voltage exceeding the voltage V-z corresponding with the intersection 2 3 is applied topoint IS.

The beam may be caused to move from one stable position to another by supplying (by means not shown) an impulse to point I6 such that the'voltage at point [6 changes abruptly to a value within the area of attraction of the desired stable position.

Siippose'the beam initially occupies the starting position 35. A'first negative current impulse at point 16 then shifts the beam to the position 23, the second impulse shifting the beam from position 23 to position 24 and so on until after six impulses position 28 is reached. In this case, the beam is adjusted to the 'left- -hand edge of the left-hand 'end aperture '1 of "the 'collectin electrode 1.

The seventh impulse causes the 'beam'back to return to the initial position '35 as follows:

The secondary-emission collecting electrode I2 is arranged at the left-hand sideof the collecting system 1, 8. The electrode l3, which is gridshaped in the present example and arranged in front of the electrode 'l2,' is locatedin the im- "inedia't'e vicinity of the said electrode 12. The electrode l3 is connected to the 'deflection'elc- 'trode'B through a capacitor l4 and furthermore connected through a resistor l5 to the positive terminal of battery H. The electro'de I2 is connected through a resistor [8' to a tap on the battery 1!. Consequently, the potentialof the electrode l3 exceeds that "of 'the'electrode [2 if the electrode ['2 is not struck by the beam. Furthermore, the electrode IZ'is coupled through 'a'capacitor to the" control "electrode 3 "which is fconne'ctedto'the cathode 2through a resistorl9. The seventh impulse shifts the "beam from the stable position at the 'left-handedge of the lefthand (and aperture 1"'of "the electrode '1 to the left so that itstrikes the electrode [2, from which secondary electrons are produced. Since the "miinber of secondary electrons leaving the elecstill further to the lefton the electrode l2. Howeve'r,the beamcannot leave'theelectrode 12 at the left ha'nd end, since in this case the'current passing to this electrode would decrease and the transmitted impulse we-111a decay.

, After 'a short-time the potential of the electrodes l2 an'dlii be'comes substantially constant.

so that no further impulse is transmitted and the capacitor C coupled to point 16 tends to discharge with the result that the beam moves again to the right i. e. in the direction of the collecting system l, 8. As soon as the beam leaves the electrode I2 the current of secondary electrons travelling to the electrode [3 terminates so that this electrode becomes rapidly discharged across the resistor l8, and a strong positive voltage impulse is produced. This positive impulse is transmitted through the capacitor I4 to the deflection electrode 6 with the result that the voltage at 19 increases rapidly to a value exceeding the voltage V5, so that the beam enters the area of attraction of the initial position 35 and assumes this position.

During its motion to the right, the beam would alternately pass through the apertures 7 of the electrode 1 and strike the electrode 8 so that an additional current would flow through the conductor 9, by which current the voltage impulse supplied through the capacitor 14 would be counteracted and the fiyback retarded. This is prevented, since the negative voltage impulse, which occurs when the electrode 12 becomes discharged, is transmitted through the capacitor to the control electrode 3. This negative voltage impulse has such a value that the beam is completely cut off during the flyback.

The flyback may be accelerated by connecting the electrode 12 to the deflection electrode 5 through a capacitor (not shown), in which event a resistor should be included in the circuit connecting the electrode 5 to the battery H.

The circuit-arrangement may be altered in various ways without departing from the scope of the invention. Thus, for example, the electrode 13 may be arranged beside the secondaryemission collecting electrode I2 and the electrode 12, instead of being coupled to a control electrode 3, may alternatively be coupled to the means 4 for producing the electron beam.

What I claim is:

1. A cathode-ray tube circuit comprising a cathode-ray tube provided with an electron gun for producing an electron beam, a collecting electrode system for said beam, deflection means coupled to said system for deflecting said beam across said system whereby said beam assumes a plurality of stable positions, a first secondary emission electrode disposed at a point in which said first electrode is struck by said beam at the extreme of its deflection and a second electrode disposed to collect the electrons emitted by said first electrode, first and second means each in. cluding a resistance for supplying first and second potentials to the first and second electrodes respectively having values at which said second potential exceeds said first potential when the beam is not in its point of extreme deflection, the potential at said second electrode being decreased when the beam is shifted to the extreme point from a stable position, means to apply input signals to said deflection means to deflect said beam, and means capacitively coupling said second electrode to said deflection means to apply the decreased potential at said second electrode to said deflection means to deflect said beam from said extreme point to its initial position.

2. A cathode-ray tube circuit comprising a cathode-ray tube provided with an electron gun for producing an electron beam, a collecting electrode system for said beam, deflection means coupled to said system for deflecting said beam across said system whereby said beam assumes a plurality of stable positions, an intensity control electrode for controlling the intensity of said beam, a first secondary emission electrode disposed at a point in which said first electrode is struck by said beam at the extreme of its deflection and a second electrode disposed to collect the electrons emitted by said first electrode, first, second and third means each including a resistance for supplying first, second and third potentials to the first, second and control electrodes respectively, said first and second potentials having values at which said second potential exceeds said first potential when the beam is not in its point of extreme deflection, the potential at said second electrode being decreased when the beam is shifted to the extreme point from a stable position, means to apply input signals to said deflection means to deflect said beam, means capacitively coupling said first electrode to said control electrode, and means capacitively coupling said second electrode to said deflection means to apply the decreased potential at said second electrode to said deflection means to deflect said beam from said extreme point to its initial position.

3. A circuit as set forth in claim 2 further comprising fourth means including a resistance for supplying a fourth potential to said deflection means, and means capacitively coupling said first electrode to said deflection electrode.

4. In a cathode-ray tube, an electron gun for producing an electron beam, a collecting electrode provided with apertures and disposed in the path of said beam, an additional collecting electrode placed behind said collecting electrode with respect to said beam, deflection means for deflecting said beam across said collecting electrode, a control electrode interposed in the path of said beam at a point adjacent to said gun for controlling the intensity of said beam, a first secondary emission reset electrode disposed at a point in which said first electrode is struck by said beam at the extreme of its deflection, and a second electrode disposed to collect the electrons emitted by said first electrode.

PIETER HENDRIK DE BEURS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,257,971 Bethenod Mar. 5, 1918 2,305,617 Hansell Dec. 22, 1942 2,463,535 Hecht Mar. 8, 1949 2,477,008 Rosen July 26, 1949 2,496,633 Llewellyn Feb. 7, 1950 2,532,738 Six et al Dec. 5, 1950 2,532,747 Van Gelder Dec. 5, 1950 2,561,057 Jonker et al. July 17, 1951 2,564,908 Kuchinsky Aug. 21, 1951 

